Last year, more than three million people fled fighting in South Waziristan and other areas in Pakistan's Federally Administered Tribal Areas. Most of these internally displaced people since have gone home.

The United Nations estimates more than one million people remain displaced.

U.N. Humanitarian Coordinator for Pakistan Martin Mogwanja says people are continuing to flee their homes because of ongoing military operations by the Pakistani government against Taliban militants in different parts of Northwestern Pakistan and he says U.N. aid agencies will need additional money.

"These are new IDPs who need, of course, new tents, new non-food item kits, new hygiene kits and indeed, the health care and so on has to be addressed. We are supporting wherever possible and where it can be done on a voluntary and sustainable basis the return of IDPs," he said. "And, we hope that, particularly in the Bajaur and Mohmand areas these IDPs will be able to return home in the coming days. But, all this is predicated upon the increased availability of resources, which is absolutely essential," said Mogwanja.

Mogwanja notes about 230,000 people fled the Federally Administered Tribal Areas in the past four months.

The United Nations appealed for $537 million for humanitarian operations from February through July and only 26 percent of that amount has been received.

U.N. Coordinator Mogwanja says this will have serious consequences for the aid operation.

"We have tried to the extent possible to preserve the life-sustaining operations-food aid, health, clean water supply and sanitation," Mogwanja said. "But, even these services are now at risk because the funding is inadequate. For example ... The World Food Program is facing a break in services at the end of June, particularly in relation to the food aid, which is being provided for food for work, school feeding programs and other early recovery activities," he added.

Mogwanja warns military operations are continuing and could expand in the tribal areas. This, he says will increase the number of IDPs. He says the humanitarian community does not have the resources to support a new caseload of displaced people that is likely to take place in the future.